To mitigate risks due to laser-induced contamination (LIC) for the LISA space mission, we have carried out an extensive LIC test campaign, including a series of short duration tests with different test parameters, as well as a long-duration test. Those previous experimental results as well as theoretical considerations indicate that LIC might be less of a concern for the LISA mission. A remaining concern is whether LIC could occur in the presence of metallic particles on optical surfaces and whether a higher pressure does have an impact. Our ongoing research thus aims at testing for a possible deposit formation in a combined LIC and metallic particulate contamination test. Therefore, a HR optics is contaminated with metallic (aluminum) particles, mounted in the sample holder and tested within a similar test setup used for previous tests. The test is performed at a pressure similar to the actual expected pressure of 10-5 mbar at the optical bench during the mission (previous tests at 10-8 mbar). These tests do not indicate that LIC is a concern and metallic particulate contaminants seem not to accelerate or trigger LIC in this laser regime.
Within the DLR project COMPASSO, optical clock and link technologies will be evaluated in space on the Bartolomeo platform attached to the Columbus module of the ISS. The system utilizes two iodine-based frequency references, a frequency comb, an optical laser communication and ranging terminal and a GNSS disciplined microwave reference. While COMPASSO is specifically dedicated to test optical technologies relevant for future satellite navigation (i.e. Galileo), the technologies are also crucial for future missions related to Earth observation and science. The optical frequency reference is based on modulation transfer spectroscopy (MTS) of molecular iodine near a wavelength of 532 nm. An extended cavity diode laser (ECDL) at a wavelength of 1064 nm is used as light source, together with fiber-optical components for beam preparation and manipulation. The laser light is frequency-doubled and sent to a mechanically and thermally highly stable free-beam spectroscopy board which includes a 20 cm long iodine cell in four-pass configuration. The iodine reference development is lead by the DLR-Institute of Quantum Technologies and includes further DLR institutes, space industry and research institutions. Phase B of the project will be finalized soon and an Engineering Model of the iodine reference, which represents the flight models in form, fit and function, will be realized by mid 2023. The launch of the COMPASSO payload is planned for 2025. Additional presentation content can be accessed on the supplemental content page.
In the past twenty years, gravimetry missions have demonstrated a unique capability to monitor not only major climate-related changes of the Earth directly from space like quantifying the melting of large glaciers and ice sheets, global sea level rise, continental draught, major flooding events, but also effects of large earthquakes and tsunamis. To respond to the increasing demand of the user community for sustained mass change observations at higher spatial and temporal resolution, ESA and NASA are coordinating their activities and harmonizing their cooperation scenarios in an implementation framework, called MAGIC (MAss change and Geosciences International Constellation). This builds upon the heritage from the GOCE, GRACE and GRACE-FO missions as well as on-going pre-developments on laser–ranging interferometry in preparation for the Next Generation Gravity Mission (NGGM). The new Laser Tracking Instrument (LTI) is being developed by the industrial lead SpaceTech GmbH with scientific lead at Albert Einstein Institute under contract to ESA. To consolidate the performance of the mission concept and the technological and programmatic feasibility of the entire mission, technology risk-retirement activities will be conducted to achieve Technology Readiness Level (TRL) 5/6 for the LTI at the end of Phase B1 and TRL 6 at the Instrument Unit level at the end of Phase A. Additional presentation content can be accessed on the supplemental content page.
We investigate effects of laser-induced contamination (LIC) with contaminant materials and laser parameters relevant for the LISA space mission. To accelerate outgassing and a possible deposit formation, the contaminant materials have been heated to a temperature of up to 100 °C (nominal operating temperature of 20° C), and LIC tests were performed with a laser power density of up to 300 W/cm2 (to be compared with expected 125 W/cm2). Neither in-situ measurements (laser transmission, polarization and wavefront), nor a careful microscopic inspection of the optical surfaces after the LIC tests showed indications of a laser-induced deposit formation. Condensation on optical surfaces could be observed. This is cautiously encouraging for LISA and indicates that the LIC concern may be reduced compared to what observed at shorter wavelength or with pulsed laser radiation.
Additional presentation content can be accessed on the supplemental content page.
Within the European Space Agency (ESA) activity “Gravitational Wave Observatory Metrology Laser” we designed a laser head to fulfill the LISA laser requirements using a non-NPRO seed laser technology: an external cavity diode laser (ECDL) with resonant optical feedback from an external cavity as master oscillator for further linewidth narrowing. Furthermore, our design features a single-stage fiber amplifier with an amplification factor of about 20 dB. This paper covers the requirements on the laser source for LISA, the design and first results of performance characterization of the laser head breadboard.
K. Nicklaus, M. Herding, A. Baatzsch, M. Dehne, C. Diekmann, K. Voss, F. Gilles, B. Guenther, B. Zender, S. Böhme, V. Mueller, D. Schuetze, G. Stede, B. Sheard, G. Heinzel
The Gravity Recovery and Climate Experiment (GRACE) is a successful Earth observation mission launched in 2002 and consisting of two identical satellites in a polar low-Earth orbit.
C. Dahl, A. Baatzsch, M. Dehne, F. Gilles, P. Hager, M. Herding, K. Nicklaus, K. Voss, K. Abich, C. Braxmaier, M. Gohlke, B. Guenther, J. Sanjuan, B. Zender, G. Barranco, A. Görth, C. Mahrdt, V. Müller, D. Schütze, G. Stede, G. Heinzel
The Gravity Recovery and Climate Experiment (GRACE) is a successful Earth observation mission launched in 2002 consisting of two identical satellites in a polar low-Earth orbit [1]. The distance variations between these two satellites are measured with a Micro Wave Instrument (MWI) located in the central axis. In data postprocessing the spatial and temporal variations of the Earth’s gravitational field are recovered, which are among other things introduced by changing groundwater levels or ice-masses [2, 3, 4, 5]. The Laser Ranging Interferometer (LRI) on-board the GRACE Follow-On (GFO) mission, which will be launched in 2017 by the joint collaboration between USA (NASA) and Germany (GFZ), is a technology demonstrator to provide about two orders of magnitude higher measurement accuracy than the initial GRACE MWI, about 80 nm/√Hz in the measurement band between 2 mHz and 0.1 Hz. The integration of the LRI units on both GFO S/C has been finished in summer 2016. The design as well as the functional, performance, and thermal-vacuum tests results of the German LRI flight units will be presented.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.